Since the first publication of Robert Louis Stevenson’s “The Strange Case of Dr. Jekyll and Mr. Hyde” in 1886, the phrase “Jekyll and Hyde” has become part of the language, denoting a person whose moral character is diametrically opposed from one situation to the next. Since its Broadway debut 20 years ago, “Jekyll & Hyde” the musical has become a cult phenomenon combining classic literature with a melodramatic pop score spawning fan clubs the world over.

The challenge for director-choreographer Paul Stancato at the Engeman Theater in this latest of a half-dozen Long Island “J&H” productions over the years is to present it with a fresh look without detracting from its core appeal.

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He and an earnest cast succeed spectacularly, led by Nathaniel Hackmann in the chemically split-personality role of Jekyll/Hyde. Dr. Henry Jekyll, frustrated by a hospital board’s refusal to endorse his laboratory experiment in separating good from evil in a human guinea pig, decides to make himself the guinea pig. The result is Edward Hyde, who proceeds to murder the entire hospital board. Jekyll becomes a stranger to his bride-to-be, played and sung by Liana Hunt with a delicate balance between devotion and determination, and to himself within his own body. Lucy, a London harlot, meets both Jekyll and Hyde, not realizing that they’re “related.” With a voice ranging from sultry to siren, Caitlyn Caughell captures Lucy’s angst in finally meeting a decent man (“Someone Like You”) while being pursued by a monster.

Hackmann electrifies on such signature numbers as “This Is the Moment” and on the climactic “Confrontation” in which his duality is brilliantly conveyed through a translucent scrim behind which Jekyll struggles to escape Hyde’s enveloping hold on his life. (Victorian set design by Stephen Dobay, dramatic lighting by Keith Truax, throbbingly amplified by Kristen Lee Rosenfeld’s band.) One quibble: The shadow effects of the sliding scrims deployed throughout the show are overused to diminishing effect, until the riveting penultimate scene.

A deep cast contributes splendidly to smaller supporting roles — among them Tom Lucca as Jekyll’s loyal friend, Jeff Williams as his prospective father-in-law, Jake Mills as the whoring bishop and Lauren Gobes as the judgmental ladyship (dazzling costumes by Kurt Alger), plus an ensemble too numerous, unfortunately, to credit here. Together they make the chorus numbers sparkle in this fine new production of a modern classic.